package com.example.code2022;

import com.alibaba.fastjson.JSON;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * @author: dangwen
 * @createDate: 2022/4/22
 * 18. 四数之和
 * 给你一个由 n 个整数组成的数组 nums ，和一个目标值 target 。请你找出并返回满足下述全部条件且不重复的四元组（若两个四元组元素一一对应，则认为两个四元组重复）
 */
public class P18 {
    public static void main(String[] args) {
        int[] nums = new int[]{2,2,2,2};
//        int[] nums = new int[]{1,0,-1,0,-2,2};
        System.out.println(JSON.toJSONString(forSum(nums, 8)));
    }

    public static List<List<Integer>> forSum(int[] nums, int target){
        List<List<Integer>> list = new ArrayList<>();
        if (nums == null || nums.length < 4) {
            return list;
        }
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 3; i++){
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            if ((long) nums[i] + nums[i + 1] + nums[i + 2] + nums[i + 3] > target) {
                break;
            }
            if ((long) nums[i] + nums[nums.length - 3] + nums[nums.length - 2] + nums[nums.length - 1] < target) {
                continue;
            }
            for (int j = i + 1; j < nums.length - 2; j++){
                if (j > i + 1 && nums[j] == nums[j - 1]) {
                    continue;
                }
                if ((long) nums[i] + nums[j] + nums[j + 1] + nums[j + 2] > target) {
                    break;
                }
                if ((long) nums[i] + nums[j] + nums[nums.length - 2] + nums[nums.length - 1] < target) {
                    continue;
                }

                int value = nums[i] + nums[j];
                int left = j + 1;
                int right = nums.length - 1;
                while (left < right){
                    if (value + nums[left] + nums[right] == target){
                        list.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
                        left++;
                        right--;
                        while (left < right && nums[left] == nums[left+1]){
                            left++;
                        }
                        while (left < right && nums[right] == nums[right-1]){
                            right--;
                        }
                    }else if (value + nums[left] + nums[right] > target){
                        right--;
                    }else {
                        left++;
                    }
                }
            }
        }
        return list;
    }
}
